This is absolutely brilliant.
Using Pokemon Showdown as your battle system feels like SO much of a COPOUT, that it somehow goes full circle into being an absolutely genius bit of creativity. Like, it retroactively makes me feel like a FOOL for not using that as the battle system for every attempt at a Pokemon one shot or campaign I've ever done. Like, Hm, what should I use to simulate a Pokemon battle? I dunno, maybe AN ACTUAL POKEMON BATTLE SIMULATOR?
I don't know how I'm going to end up using this design philosophy in my own rpg games going forward, but I KNOW that I will.
Congratulations on making the best Pokemon TTRPG I've ever seen.